Phenobarbital is known to be a potent inducer of liver microsomal enzymes and in the primate has been shown to increase bile flow rate, bile salt and phospholipid secretion, and decrease the proportional cholesterol content of bile. To evaluate further its effects on biliary lipid secretion and metabolism the relative composition of bile, hepatic secretion rates of biliary components, bile acid synthesis and pool size have been determined in normal subjects before and after phenobarbital administration. The experimental work has been completed and the data have been prepared for publication.